1. Field of the Invention
The present invention relates to magnetic alloys especially to iron-aluminum-silicon alloys.
2. Description of the Invention
Fe-Al-Si (iron-aluminum-silicon) alloys i.e. sendust alloys have such feature that the alloys are high in permeability .mu., great in saturation induction Bs and small in coercive force H.sub.c, and also since the alloys are high in Vickers hardness, they are suitable for use as a core material of a magnetic head. Especially, recently high density recording has been promoted, and in case of a magnetic recording medium using a magnetic material with high coercive force, such magnetic heads, which will record a signal on the above magnetic recording medium and erase the recorded signal thereon, are required to be made of a core material with especially high saturation induction Bs. As the core material of the above magnetic head, the Fe-Al-Si alloys become into the spotlight. However, the Fe-Al-Si alloys are very brittle and hence it is almost impossible to subject the alloys to forging and rolling processes.
In order to provide a laminated core, which will be used to produce a magnetic head having a narrow track width or to improve the deterioration of high frequency characteristic of a magnetic head for a video signal (high frequency signal), which is caused by eddy current loss, it is necessary that Fe-Al-Si alloys are worked to be a thin plate. In general, in order to work such a kind of alloys to a thin plate, an ingot which is made by casting not by forging or rolling is sliced and then polished to be a desired thin plate.
Since the ingot is damaged easily due to its brittleness and internal stress is generated therein by the above method frequently, the above method is not satisfactory for mass-production.
The sendust alloys were reported on pages 127 to 135, vol, 1 (1937) of Journal of Japan Institute of Metals of the thesis on "Magnetic and Electrical Properties of New Alloys `Sendust` and Fe-Al-Si Alloys" and many tries to improve the sendust alloys have been carried out for 40 years or more. The tries can be generally classified as the following two kinds. One is to improve the magnetic property as well as wear resistance, workability and corrosion resistance of the sendust alloys by adding a suitable element thereto and the other relates to the method of making and working this kind of alloys. As one example of the former, there is proposed a wear resistance high permeability magnetic alloy containing as main component, 3.0 to 13.0 weight % of Si and 3.0 to 10.0 weight % of Al and remaining Fe added with 0.1 to 7.0 weight % of Y which are melted and then hardened as disclosed in the Japanese published unexamined patent application No. 88418/76. Further, the Japanese published unexamined patent application No. 88419/76 discloses, as the wear resistance high permeability magnetic alloy, an alloy which contains as main component 3.0 to 13.0 weight % of Si, 3.0 to 10.0 weight % of Al and Fe alloy containing 0.1 to 7.0 weight % of Y and 0.1 to 3.0 weight % of at least one of Ti, Zr and lanthanide elements. Also, the Japanese published unexamined patent application No. 115696/76 discloses a wear resistance high permeability alloy which contains 3 to 13 weight % of Si, 3 to 13 weight % of Al, 0.01 to 7 weight % of Ce and the remaining part being Fe as its main component, and the Japanese published unexamined patent application No. 145421/76 discloses a wear resistance high pemeability magnetic alloy which contains 5 to 12 weight % of Si, 4 to 8 weight % of Al, 0.05 to 6 weight % of Ce, 0.1 to 3 weight % of at least one element of Ti, Zr and lanthanide elements (except Ce) and the remaining part of Fe as the main component, and the Japanese published unexamined patent application No. 128618/76 discloses a wear resistance high permeability magnetic alloy which contains 3.0 to 13.0 weight % of Si, 3.0 to 13.0 weight % of Al, 0.01 to 7.0 weight % of La and the remaining part of Fe. Further the Japanese published unexamined patent application No. 4420/77 discloses a wear resistance high permeability magnetic alloy which contains, as its main component, 3 to 13 weight % of Si, 3 to 13 weight % of Al, 0.01 to 7 weight % of La, at least one element of Ti, Zr and lanthanide elements (except Ce and La) and the remaining part of Fe, and the Japanese published unexamined patent application No. 41622/76 discloses the method of making a magnetic alloy whose wear resistance is improved by which 6 to 12 weight % of Si, 3 to 8 weight % of Al and 80 to 91 weight % of Fe are added with 0.3 to 7 weight % of Ti and the resultant mixture is subject to a suitable thermal treatment. The Japanese published unexamined patent application No. 56397/77 discloses a wear resistance high permeability magnetic alloy which contains, as its main component, 2 to 9 weight % of Al, 4 to 12 weight % of Si, 2 to 16 weight % Cr and the remaining part of Fe. The Japanese published unexamined patent application No. 119298/75 discloses a corrosion resistance high permeability magnetic alloy containing, as its main component, 2.5 to 17 weight % of Al, 4 to 16 weight % of Si, 0.2 to 15 weight % of Cr, 0.2 to 10 weight % of Ni and the remaining part of Fe. The Japanese published unexamined patent application No. 94822/77 discloses a non-brittle high permeability magnetic alloy which is provided by adding 0.01 to 4.5 weight % of Ti and 0.005 to 1.5 weight % of C to a sendust alloy or sendust alloys, and the Japanese published unexamined patent application No. 30388/76 discloses that it is possible that a magnetic alloy for magnetic head of 3 to 8 weight % of Si, 2 to 5 weight % of Al, less than 6 weight % of Ni and the remaining part of Fe can be made as a thin plate with the thickness of 0.05 mm by hot rolling. While, as read on "The Magnetic Characteristics of `Super Sendust (II)` of Fe-Si-Al-Ni Alloys" on page 179 of Proceeding of Autumn Conference on Magnetics held 1978, an alloy consisting of 4 to 8 weight % of Si, 2 to 6 weight % of Al, 0 to 7 weight % of Ni and the remaining part of Fe can be subjected to warm rolling and also is superior in magnetic property but its Vickers hardness H.sub.v, which is intimate to the wear resistance property, is 410 which is lower than the prior art sendust alloys by about 100. The Japanese published unexamined patent application No. 121427/76 discloses such an alloy consisting of 3 to 8 weight % of Si, 2 to 5 weight % of Al, not more than weight % of Ni and the remaining part of Fe which can be rolled to a thin plate having the thickness of 0.2 mm by hot rolling and cold rolling. The Japanese published unexamined patent application No. 138012/77 discloses a magnetic alloy consisting mainly of 3 to 8 weight % of Al, 3 to 12 weight % of Si, 0.01 to 5 weight % of Y and the remaining part of Fe whose workability, wear resistance and corrosion resistance are improved.
Meanwhile, as to the latter i.e. method of making the sendust alloys and working method thereof, there are a number of reports. For example, according to "The High Purity Sendust and its Application to a Magnetic Head" described on pages 75 to 80, August, 1977 of the magazine "Denshi-zairyo (Electronic parts and Materials)", it is possible after closely examining the material of the sendust that a sendust ingot good or with a uniform grain structure and without defect, pin holes and residual strain can be made by vacuum centrifugal casting. The Japanese published unexamined patent application No. 38097/75 discloses such a method in which a raw meterial with the alloy composition of 8 to 11 weight % of Si, 4 to 8 weight % of Al and 83 to 86 weight % of Fe is melted and cast, then ground as powders, and the powders are molded and then the molded material is hot pressed at 900 to 1250.degree. C. under the pressure more than 150 kg/cm.sup.2 . Further, in the thesis "Powder Rolling Method of Sendust Alloy and Electromagnetic Characteristics Thereof" on pages 20 to 27 of Journal of the Japan Society of Powder and Powder Metallurgy Vol. 14, January, 1967 there is a description that mechanically crashed powders and spray cooled powders are subjected to the powder rolling to provide a sendust sheet having the thickness of 0.6 to 0.8 mm. The Japanese published examined patent application No. 26505/77 discloses the fact that a sendust alloy ingot is sealed in a sheath member through a heat insulator, heated at the temperature range of 900.degree. to 1100.degree. C., and then rolled by 15 times of rollings from the thickness of 5 mm to be the thickness of 0.23 mm. Further, in the thesis "mechanical and magnetic properties of few hot forged Fe-Al-Si alloy" on pages 922 to 926, vol. 37 No. 8 (1973) of Journal of the Japan Institute of Metal, there is such a description that after the sendust consisting of 6.44 weight % of Al, 10.32 weight % of Si, 0.68 weight % of Ti and the remaining part of Fe is subjected to the bending test and sheath forging test by a thin sheath member at 800.degree. to 1000.degree. C., 70% of deformation due to compression can be given thereto by forging at 1000.degree. C. and plastic deformation appears therein even at 800.degree. C. The Japanese published unexamined patent application No. 123919/77 discloses a method where a melted alloy whose main component is Fe-Al-Si is cast in a chilled mold, whole the ingot is cooled at the cooling speed higher than at least 200.degree. C./min. to provide a high grade ingot. In "manufacturing of sendust sheet by the spark sintering and the electromagnetic property thereof" on pages 5 to 13, Vol. 15, No. 1 (1968) of Journal of the Japan Society of Powder and Powder metallurgy, there is reported the fact that a sendust sheet can be made by spark-sintering a powder consisting of 5.38 weight % of Al, 9.26 weight % of Si and the remaining part of Fe and having the grain size of 325 mesh. The Japanese published unexamined patent application No. 56313/75 discloses such a method in which the powders of an alloy consisting of 5 to 12 weight % of Si, 3 to 8 weight % of Al and the remaining part of Fe are sealed in a can and then is subjected to the hot extrusion at the temperature range of 900.degree. to 1280.degree. C. with the ratio of rolling reduction more than 3 to make an alloy whose grain size is smaller than 30 .mu.m. The Japanese published unexamined patent application No. 138517/76 discloses such a method in which levitated Fe-Al alloys or Fe-Al-Si alloys by high frequency induction heating is made as a thin plate by a steel roll, and the Japanese published unexamined patent application No. 123314/77 discloses a method of making ribbon shaped sendust alloys.
As described above, there are investigations which will improve superior various magnetic properties of the Fe-Al-Si alloys and also improve their mechanical property such as workability, wear resistance, corrosion resistance and so on, and also there are many investigations and reports which work the alloys with a desired shape without loosing their superior magnetic properties by developing the special melting method, working method and molding method.
However, up to now there has not been proposed Fe-Al-Si alloys in the art which have superior magnetic properties, are superior for mass-production and yield, capable of being forged and rolled to be made into a sufficiently thin plate.